Free antivirus software have certainly come a long way, and can no longer be ignored on grounds of incompetence. I've had free antivirus succeeding in situations where the big names all gave way. Here are the top 3 antivirus software:

avast! Home EditionAlwil product page | topThe latest version of avast (v4.7.1098) is reportedly very good. I have friends who are long time users of avast, and they're happy with it. I myself used it for a couple of weeks. It's good: it has a good boot-time scanner, and it's much better catching viruses and malware now. It's light on system resources, too. avast is clearly the best free antivirus out there, although I can't really say it's as good as a decent paid antivirus (it did, however, catch worms that Norton and an older version of McAfee missed). avast's download servers aren't the best (or at least the ones they have in Asia aren't); like all free antivirus software, their real-time scanner needs improvement; and once it's running on your PC you'll get lots of false alerts (mostly update-related). I had a very weird problem with a previous version of avast (v4.6; I forgot to test it on the latest one): I use a DD-MM-YY date format on my computer, but avast seems to recognize only MM-DD-YY. As a result I couldn't use the software after a point; avast kept reminding me that my license had expired. I wrote to Alwil (the company) about it more than once, but didn't get a reply. The problem wasn't fixed in the upcoming weeks, so I decided I had had enough. The avast icons, spinning on their own (one of them) in the system tray, is a sight that I can't stand (why do you need to have spinning, bloated-looking icons?). And although avast has many skins available, the interface needs to be much more intuitive.Summary: decent detection rate, light on system resources; poor interface, support is poorPrice: free

Avira AntiVir PE ClassicAvira product page | topLet me put it this way: AntiVir is a good free antivirus, but it suffers from some issues avast doesn't. (I felt) AntiVir had a better detection rate than avast (contrary to the reviews you'll read), or is just as good. The interface is nice, the red umbrella icon is pleasing, and the real-time scan is definitely better than avast. The latest version (v7.06.00.268) is, unfortunately, buggier than the previous one. My MSN Messenger refused to run anymore once I installed AntiVir; the website is agonizingly non-intuitive; it takes ages to run the complete scan, and worse, it alerts you when it finds a virus and refuses to move on until you've specified an action. The last feature alone is enough to turn off many users.Summary: good/decent detection engine, nice interface; buggy, slow scan speed, have to treat infections one at a timePrice: free

AVG Anti-Virus Free EditionAVG Technologies product page | topAVG is, quite frankly, the most popular free antivirus out there. According to reviews, it has a good detection rate and offers solid protection. From my experience, it's horrible, and its popularity and critical acclaim (5 stars by CNet and a VB100% award) is one of my great software junkie mysteries. It can't catch viruses, and seems to avoid malware altogether. It's not really RAM intensive, but definitely is heavier on system resources compared to AntiVir or even avast. AVG Technologies (formerly Grisoft) isn't really responsive to virus outbreaks, and the updates dealing with a particular situation often appear too late. Last but not the least, the interface gets the job done, but seriously, seriously needs cosmetic surgery.Summary: poor detection rate, updates aren't up-to-date, ugly interfacePrice: free

Conclusion | topIt's clear that the bigshots in the game are rapidly losing ground. McAfee and Norton users are already switching to newbies like Kaspersky. Kaspersky, NOD32, F-Secure and BitDefender are all excellent software, although excessive RAM consumption seems to be an incurable trait of antivirus applications themselves. It's also interesting to note that it's getting harder to pinpoint a clear winner anymore -- the distinction between a good and great antivirus is not so distinct. I'm especially surprised at McAfee's situation: in recent times they've come up with a great Site Adviser tool that enjoyed tremendous popularity, but the company simply hasn't managed to cash on it.

All the big names in the antivirus arena have flopped big time. McAfee still suffers from a stupid interface and RAM consumption issues, Norton has its bugs and uninstallation problems and Trend Micro's track record is so bad of late that nobody's even bothered to give it a try. Some antivirus software that have been around for a while, such as Panda, are yet to hit the mark. Kaspersky is clearly poised to become the next major antivirus brand. It's received excellent reviews and users are rarely unhappy with it. The only competitor that can really be a threat to Kaspersky is NOD32, which has perhaps already surpassed Kaspersky's virtues. BitDefender has suddenly raised the bar for all antivirus software by offering a substantially cheaper price tag. You can almost be sure there'll be a trend of all major brands being forced to lower prices as well, which is a good thing for us users. Kaspersky needs to lower its price if it wants to hold on to its ambitions, and F-Secure will remain as underrated if it doesn't come cheaper.

On the free front, my advice: don't use free antivirus software unless you absolutely have to. Despite what you might have heard or read, they're not as good as their paid counterparts. Real-time scanning is an area they need to concentrate on, and the lack of finesse they all seem to suffer from is something that should have been solved a long time ago. If you're absolutely cash-strapped, tryout avast and AVG to find out which best suits you.

I missed out on some brands: CA (formerly eTrust EZ Antivirus), Comodo and BitDefender Free. I haven't tried any of them, although it's worth pointing out that Comodo is still in beta and BitDefender Free is only an on-demand scanner. You can also scan your computer for viruses free online from Trend Micro, Panda, and BitDefender websites; I tried Trend Micro and BitDefender's online scans but they always terminated prematurely due to one issue or another.

All that being said, it really depends on what antivirus best suits your computer. Read the reviews and decide for yourself. If I were you, I'd go for NOD32. I currently use Kaspersky but am planning not to renew my subscription, due to the problems I mentioned. If you're on a budget, go for BitDefender.